Advertising manager improvements

* Keep track wether advertiser is enabled.
* Make sure that random address for connectable advertisers is updated
  when advertising is disabled, as per ESR11-E7716.
* Make sure that the local variable holding the address is properly
  updated after the address is pushed to the controller.
* Use "LE Remove Advertising Set" command to free advertiser after use.

Bug: 35935853
Bug: 30622771
Test: manual
Change-Id: I1415f7272dd99e5e81ce1e2b7ef2bf98f7229cf9